SEARCH · Search PubMed

Results for “VISCOSITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,711 records · Page 95Linked to original sources

PubMed1997

Relationship between autonomic function and plasma fibrinogen, viscosity, and elements of fibrinolytic activity in diabetic nephropathy.

Twenty-three insulin-dependent diabetics with proteinuria (3.3 g/day: range 0.3 to 8.9) and azotemia (creatinine clearance: 58 mL/min, range 30 to 112) were tested for 24-h mean arterial blood pressure; instantaneous heart rate variations to a computerized protocol involving timed ventilation, assumption of upright posture, and Valsalva maneuver; plasma fibrinogen, viscosity, fibrinolytic activity, and plasminogen activator inhibitor. These were to test the hypothesis that autonomic dysfunction is associated with altered concentrations of plasma fibrinogen, fibrinolytic activity, viscosity, and plasminogen activator inhibitor. We have previously shown the absence of a correlation between level of blood pressure, clinical and standard laboratory testing, and the results of the autonomic function testing protocol used in this study. In this group of patients, plasma fibrinogen concentration was correlated (positively) with mean arterial pressure and (negatively) with heart rate variation in response to the Valsalva maneuver. The greater the mean arterial pressure or the worse the Valsalva results, the higher the plasma fibrinogen concentration. In addition, patients with one or no abnormal autonomic function tests had a mean fibrinogen of less than 400 mg/dL compared to the group of patients with two or more abnormal tests who had a mean fibrinogen of 500 mg/dL. In patients with demonstrated parasympathetic abnormalities, postural heart rate variation testing also discerned a differential in plasma fibrinogen. Lower concentration of plasminogen activator inhibitor throughout the day, and greater fibrinolytic activity in the morning were also noted to be present in patients with abnormal heart rate response to the Valsalva maneuver. We conclude that there are relationships between high blood pressure, autonomic function, and hemostatic factors favoring thrombogenesis that may be related by common mechanisms and treatments in the diabetic with kidney disease.

Adult↗

PubMed1977

[Blood viscosity and triglyceridemia. Findings using a co-axial cylindrical viscosimeter at low "shear rates"].

Examination of blood viscosity at low shear rates using a co-axial cylinder viscometer showed a significant difference between the means of values observed in hypertrigliceridemic patients compared with that of control subjects. This result differs from what has been reported by most workers although generally greater shear rates have been used. Calculation of the "r" coefficient and plotting of the regression line for each shear rate showed that there is no linear correlation between blood viscosity and triglyceridaemia, whose variations occur quite independently. It is suggested that the absence of a correlation between the two parameters examined may depend on various factors, of which the most important are those pertaining to the rheological properties of red blood cells and to the structure and chemical and physical characteristics of the triglyceride molecule and of the lipoproteins and chylomicrons which transport them.

Blood Viscosity↗

PubMed1977

[The effect of low fibrinogen concentrations on human blood viscosity].

Simultaneous studies of viscosity, red cell aggregation and deformation were carried out on human blood with different fibrinogen concentrations using a Brookfield viscometer fitted with a reflection photometer. Fibrinogen progressively increased rouleaux formation, while decreasing viscosity at low and increasing it at higher concentrations. This antagonism is explained by the specific hemodynamic effects of the rouleaux formed under either condition.

Afibrinogenemia↗

PubMedDate not supplied

The effect of long-term treatment with hypotensive drugs on blood viscosity and erythrocyte deformability in patients with essential arterial hypertension.

This study examined ninety-six patients with essential arterial hypertension (WHO grade I-II) who had been under treatment for a period of at least one year before participating in the study. When the study began the patients received no drug treatment for one month. At the end of this washout period their basal situation was evaluated and drug treatment was begun (26 patients on calcium antagonists, 39 on beta-blockers and 31 on angiotensin converting enzyme inhibitors). The patients were evaluated again after one and two years of uninterrupted treatment with the chosen medication. The results obtained indicate that in a basal situation hypertensive patients have higher blood viscosity and erythrocyte rigidity values than the control group. Regardless of the drug treatment used, the patients experienced during the study a progressive deterioration of their hemorheological situation consisting of an increase in red blood cell rigidity and increased blood viscosity. These results indicate the importance of evaluating the hemorheological parameters of hypertensive patients and suggest that it may be advisable to include in their treatment some kind of medication that prevents progressive rheological deterioration.

Adrenergic beta-Antagonists↗

PubMed1997

[Blood viscosity disorders as an etiopathological factor in sudden deafness].

Because idiopathic sudden deafness is regarded as the result of a cochlear microcirculation disorder, its treatment has been based mainly on vasoactive therapy with little regard for the blood-flow conditions produced by these circumstances. In a group of 16 patients with sudden-onset deafness, we determined blood viscosity at different shear rates, as well as erythrocyte aggregability, deformability, and filterability, and other potentially influential parameters, such as hematobrit, fibrinogen, and leukocyte and platelet count. These values correlated with hearing loss and average recovery after conventional treatment. Our results showed a trend to high blood viscosity in patients in relation to a control group of persons with normal hearing, with a notorious increase in aggregability, which correlated significantly with recovery of hearing capacity, and a decrease in blood filterability, which correlated with average hearing loss. This suggests a potential etiopathogenic mechanism of the disease and an alternative treatment complementary to current treatment.

Anti-Inflammatory Agents↗

PubMed1998

The role of the contrast medium viscosity in the adequacy of operational cholangiography.

The viscosity of some routine hydrosoluble contrast media used in operational cholangiography (Bilignost and Verographin) was studied. The different viscosity of hepatic and vesical bile and of the contrast media was determined. This fact shows that the data of any direct cholangiography in accordance with the law of Hagen-Poiseuille is misinterpreted. As a result it may lead to a wrong surgical procedure, for example, sphincterotomy, and vice versa.

Cholangiography↗

PubMed1998

No influence of furosemide on human erythrocyte shape and volume and blood viscosity in vitro.

Furosemide is a diuretic agent which is often given in high concentration intravenously. Since erythrocytes have a furosemide-sensitive transport system and oral application of furosemide was found to induce an echinocytic shape transformation in horses, we have analysed the influence of furosemide on erythrocyte shape, volume and blood viscosity in vitro. Increasing plasma furosemide concentrations of 0, 1, 10, 100 and 1000 micrograms/ml did not affect the erythrocyte volume or shape and left blood viscosity unaffected. We conclude that furosemide has no influence on blood rheology in humans.

Administration, Oral↗

PubMed1976

Plasma protein changes, blood viscosity, and diabetic microangiopathy.

Diabetic microangiopathy is a slowly progressive condition that usually manifests itself years after the onset of the carbohydrate-metabolism disturbance. It is a far more striking problem in some diabetics than in others. Differences in the pattern of its effect in several body systems suggest that the local vascular disturbance is a mixture of a general microcirculatory change in diabetes and a specific vascular alteration in each tissue. Its manifestations in the individual diabetic appear to be influenced by both elements. Evidence is presented that plasma protein changes in diabetes and their effects on blood flow play a role in acclerating the rate of progression of diabetic microangiopathy by raising plasma viscosity and by increasing the affinity of erythrocytes for each other. The plasma protein change is dominated by a possibly hormonally mediated pattern of alpha-globulin elevation seen in many chronic disorders. This elevation of acute-phase proteins is not likely by itself to produce diabetic microangiopathy, but it may cause an additional stress on the metabolically disturbed diabetic microcirculation. The basic change is a disturbance in the average molecular shape of the plasma proteins that both directly increases plasma viscosity and enhances the aggregation of erythrocytes. Studies are now in progress to determine which of these two mechanisms is more likely to be important in accelerating the development of diabetic microangiopathy.

Blood Flow Velocity↗

PubMed1976

[Influence of isoxsuprine HCl on blood viscosity].

A decrease of blood viscosity is a working principle in the therapy of severe disorders of arterial blood flow. Isoxsuprine-HCl was found effective in lowering the blood viscosity when given intravenously in a dose of 30 mg over 60 min. This effect derives probably from a decrease of the tendency to aggregate and an increase of the flexibility of red blood cells. 30 min after termination of the infusion this effect has its maximum and 60 min later still is significantly raised.

Blood Viscosity↗

PubMed1996

Viscose cellulose sponge as an implantable matrix: changes in the structure increase the production of granulation tissue.

Since the 1950s a number of implantable substances have been used to study granulation tissue formation: steel mesh, polyvinylalcohol (PVA), polytetrafluoroethylene (PTFE), polyurethane, and viscose cellulose sponges (VCS). The side effects of these materials on granulation tissue formation vary considerably. An ideal material does not interfere with the normal wound-healing process and collects as many cells as possible for further analysis. Viscose cellulose sponge has been shown to be one of the most inert materials for this purpose. In this study we examined the correlation between changes in the structure of the sponge and the number of cells harvested and the synthesis of granulation tissue after subcutaneous implantation in rats. It was discovered that it is possible to control the structure of the sponge and by certain changes in this structure increase the number of invading cells and the production of granulation tissue in the sponge. There is, however, a distinct plateau after which changes in structure do not increase the number of invading cells and the production of granulation tissue in the sponge.

Animals↗

PubMed2003

Rapid separation and laser-induced fluorescence detection of mutated DNA by capillary electrophoresis in a self-coating, low-viscosity polymer matrix.

The detection of point and other simple mutations in DNA is important for cancer research and diagnosis and other biological studies. Capillary electrophoresis has been successfully used for separating DNA fragments. However, a low-viscosity polymer sieving buffer for DNA separation with on-line coating has never been reported. In this paper, a new method using capillary electrophoresis with on-line coating and laser-induced fluorescence detection (CE-LIF) for screening for point or simple DNA mutations has been demonstrated. The method uses an on-line dynamic coating technique that increases capillary lifetime and analysis reproducibility, and employs a low-viscosity polymer solution, which allows the user to rinse the capillary rapidly and refill with polymer solution easily. Experiments proved that the additives in the separation buffer for on-line capillary coating do not affect the separation efficiency of the running buffer, and do not interfere with the formation of hydrogen-bonded network between boric acid, mannitol and hydroxypropylmethylcellulose polymers. The stability of the dynamically coated capillary was quantitatively studied; the capillary lifetime was increased 6- to 7-fold compared with that of permanently coated CE columns. Standard DNA fragments containing mutations, with sizes of 209, 219, and 338 bps, were successfully separated and detected with this system, after the mutated DNA fragments were cleaved by CEL-I endonuclease. The technique is very sensitive for the size-separation of low-range, middle-range, and high-range DNA fragments. Results were compared with the HPLC methods developed by Transgenomic, Inc. and were in good agreement. The method should be applicable to mutation detection for all relevant biological and clinical studies. The factors influencing separations and the stability of dynamic capillary coatings are also discussed in the paper.

Boric Acids↗

PubMed2000

Drag of a Solid Particle Trapped in a Thin Film or at an Interface: Influence of Surface Viscosity and Elasticity.

We propose a theoretical model for the motion of a spherical particle entrapped in a thin liquid film or in a monolayer of insoluble surfactant at the air/water interface. Both surface shear and dilational viscosity, surface diffusion, and elasticity of the film are taken into consideration. The drag force acting on the particle is analytically calculated and asymptotic expressions of the problem are provided. The relevance of the model is discussed by comparing the calculated "viscoelastic" drag, gamma(vel), to the one predicted by Saffman's theory, gamma(S), for cylindrical inclusions in membranes. Numerical analyses are performed to evaluate the contributions of the surface viscosity and the diffusion coefficient of the layer on the hydrodynamical resistance experienced by the particle. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Liquid Bridge between Two Moving Spheres: An Experimental Study of Viscosity Effects.

The effects of viscosity on the mechanical response of a liquid bridge are investigated in the case of small amounts of liquid axially strained between two moving spheres. An experimental setup allows the measurement of capillary and viscous forces exerted on the spheres as a function of the spheres separation distance and the spheres velocity. The experimental results are found to be accurately described over a large range in spheres velocity and liquid viscosity by a simple closed-form expression. In addition, the bridge rupture distance is found to increase like the square root of the separation velocity. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Population viscosity and the evolution of altruism.

The term population viscosity refers to limited dispersal, which increases the genetic relatedness of neighbors. This effect both supports the evolution of altruism by focusing the altruists' gifts on relatives of the altruist, and also limits the extent to which altruism may emerge by exposing clusters of altruists to stiffer local competition. Previous analyses have emphasized the way in which these two effects can cancel, limiting the viability of altruism. These papers were based on models in which total population density was held fixed. We present here a class of models in which population density is permitted to fluctuate, so that patches of altruists are supported at a higher density than patches of non-altruists. Under these conditions, population viscosity can support the selection of both weak and strong altruism.

Altruism↗

PubMed2001

Increased viscosity is protective for arteriolar endothelium and microvascular perfusion during severe hemodilution in hamster cheek pouch.

We hypothesized that during severe hemodilution (SH), i.e., hemodilution beyond 50%, the reduced conditions of shear stress result in endothelium dysfunction and subsequent vasoconstriction. To evaluate the endothelial responses associated with the reduction of hematocrit we tested the responsiveness of arterioles to acetylcholine. Infusion with high-molecular-weight dextran 500,000 following SH was characterized by laser Doppler flowmetry (LDF), total perfused capillary length (TPCL), vessel diameter, and red blood cell (RBC) velocity as visualized by fluorescence microscopy in the hamster cheek pouch. Hemodilution was performed by blood removal and simultaneous infusion of 6% dextran 70. LDF increased significantly during hemodilution in arterioles and in venules (100 +/- 20 vs 37 +/- 11 and 34.2 +/- 3.5 vs 28.6 +/- 4.0 perfusion units, PU, respectively). During the final step of hemodilution LDF decreased significantly to 12 +/- 4.5 PU in arterioles and 6.2 +/- 1.5 PU in venules, which correlated with the decrease of arteriolar RBC velocity. Arterioles constricted and TPCL decreased significantly (-35 +/- 5.3%). Hyperviscosity infusion significantly raised arteriolar and venular LDF to 184 +/- 15 and 40.2 +/- 3.5 PU, arterioles dilated, RBC velocity, TPCL, and mean blood pressure. There was an impairment of endothelial-dependent dilation that was not present in the group with dextran 500, which suggests that viscosity was involved in the development of vasoconstriction during SH. In conclusion, an increase in plasma viscosity has beneficial effects on the microcirculation during SH that might preserve arteriolar endothelium and capillary perfusion.

Animals↗

PubMed1980

Red cell flexibility, electrical resistance and viscosity of blood flowing through small glass capillaries.

The influence of varying shear forces (4-10 microN.cm-2) generated by a pulsating flow of 4 cycles/min, on the longitudinal electrical resistance (R) of a blood perfused small glass capillary (I.D. = 0.12 mm, l = 30 mm) was determined. Red cells were stiffened by stepwise addition of bile or by sterile incubation during 24-48 h. The shear dependent changes in R were closely related to red cell flexibility and apparent blood viscosity. In normal defibrinized blood R decreased by about 3%, while more rigid cells evoked a shear dependent increase in R of 1-5%. The measurements performed demonstrate that the typical shapes of the electrical signals provide more information of rheological significance of red blood cell flexibility than the results of viscosity determination alone.

Blood Circulation↗

PubMed1997

Effects of exposure to carbon disulfide (CS2) on electrocardiographic features of ischemic heart disease among viscose rayon factory workers.

The objective of the study was to evaluate viscose plant workers for electrocardiographic manifestations resulting from exposure to carbon disulfide (CS2). A total of 162 workers (118 in an exposure group and 44 in a reference group) were evaluated using a health questionnaire, physical check-up, biochemical analysis of blood samples and electrocardiograms (ECG). The exposure group consisted of workers in the following areas: viscose manufacturing, cellophane processing, ripening, and filament spinning. Reference group workers were from the administrative office, rolling area, pulp processing, and testing office. Only slight differences were found in the biochemical analyses of the two groups, with the exception of sodium (Na) levels. Personal and area sampling results were found to have a high variation due to different locations within the plant and a wide range of manufacturing processes. Highest CS2 concentrations were found in the ripening area (54.60 ppm) and the filament spinning area (19.60 ppm). Using a multiple logistic regression model to control variables (age, gender, body mass index, duration of employment, cholesterol, smoking, and alcohol), we found a relative risk for ECG abnormalities 4.18 times significantly higher for the exposure group. The authors feel that the installation of an adequate ventilation system could greatly reduce the risk of workers developing CS2-induced cardiovascular abnormalities.

Adult↗

PubMed1995

Epidemiological study of eye irritation by hydrogen sulphide and/or carbon disulphide exposure in viscose rayon workers.

In the framework of an extensive health survey 123 male viscose rayon workers exposed to hydrogen sulphide (H2S) and/or carbon disulphide (CS2) and 67 referents not exposed to either of these chemicals answered questions on eye irritation complaints in a self-administered questionnaire. Personal exposure varied from 4 to 112 mg m-3 for CS2 and from 0.2 to 8.9 mg m-3 for H2S. A combined exposure measure was calculated using principal component analysis. The exposed subjects had a significantly higher prevalence of eye pain, burning and photophobia. Adjustment for age and smoking in logistic regression revealed significantly more eye complaints for all workers that were highly exposed. In a postal survey one-third of the ex-workers of the same viscose rayon factory reported having left the factory because of eye complaints, indicating that their occurrence may be underestimated in the cross-sectional study.

Adult↗